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Diciembre 2009 |
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Conferencias del Dr. Bernard Gersh |
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Muerte súbita (MS) e isquemia Dr. Bernard Gersh El Dr. Gersh comenzó
la conferencia estableciendo que en los estudios de pacientes portadores de
cardiodesfibrilador (CDI) se observa una incidencia de TV/FV de 52% aprox.
Para establecer la
importancia del tema, comentó el estudio “Long term survival of out of
hospital arrest after succesfull defibrillation”, publicado en New England Journal of Medicine,
sobre 200 pacientes con FV presenciada, de los cuales sólo 72 llegaron al
hospital, y de éstos sólo el 40% fue dado de alta sin alteraciones neurológicas
significativas. De los pacientes que sobrevivieron al alta y que fueron
revascularizados, 43% presentó nuevos episodios de TV/FV. Es decir, el tratamiento de la isquemia en
la prevención secundaria, aunque necesario, no es suficiente para prevenir nuevos
episodios de MS.
Con respecto a la prevención
primaria de la MS en la cardiopatía isquémica, mostró numerosos ensayos centrando
su análisis en los estudios Dinamit y CABG Patch, que fueron los únicos que
tuvieron resultado negativo o neutro acerca del beneficio del uso de CDI para
prevención de MS.
El estudio CABG Patch,
publicado en 1996, fue neutro. Este estudio mostró beneficio de la revascularización
para la prevención de la MS. Sin embargo, el efecto protector de la
revascularización ocurre en la etapa temprana, perdiéndose a partir del primer
año. Por el contrario, los efectos positivos de los CDI en todos los ensayos (principalmente
MADIT II) fueron evidentes a partir de los 18 meses. El ensayo Dinamit randomizó
pacientes postinfarto de miocardio con disfunción sistólica a implante de CDI
si/no. Este estudio mostró que la mayor incidencia de MS postinfarto se
presenta en los primeros 30 días postinfarto. La incidencia MS fue reducida
por el CDI y los resultados se explican por la incidencia aumentada de muerte
no arrítmica. Buscando una explicación
mostró un estudio autópsico (Orn y cols. American Journal of Medicine, 2005) en
el que se estudiaron pacientes con IAM en los 10 días previos; solo el 14%
murió por MS, en tanto 52% murieron por reinfarto y el resto por falla
cardíaca. Interrogados los CDI en estos pacientes se comprobó que los choques
administrados fueron debidos a situaciones de arritmia como expresión final
de un proceso de muerte por otras causas. Es decir que las arritmias fueron
una vía final de los otros procesos. En cambio en los pacientes con MS cardíaca
tardía postinfarto los episodios de MS son mayoritariamente arrítmicos.
En cuanto a la
estratificación de riesgo, estableció que: a) la
alternancia de onda T parece ser un estudio promisorio, pero es difícil
definir a qué grupo de pacientes y en qué momento realizarlo. b) la
disfunción sistólica continúa siendo el elemento de mayor valor. La
incidencia de MS aumenta con la evolución de IC. Finalmente hizo
mención a la variación circadiana de la presentación de la MS: 24% de los
episodios son de la hora 22 a la hora 6, 45% de 6 a 14 y 32% de 14 a 22 en la
población global. Sin embargo, en los pacientes que tiene alteraciones respiratorias
del sueño el 54% de los episodios de MS se presentó de 22 a 6. La misma
variación se repite respecto de la incidencia de infarto. Finalizó su
conferencia haciendo referencia el trabajo publicado por Goldenberg en JACC en
2008 que establece un score de riesgo de MS. Las variables que se relacionan
con mayor riesgo son: insuficiencia cardíaca von clase funcional mayor a 2, fibrilación
auricular, ancho de QRS mayor a 120 mseg, edad mayor a 70 años e insuficiencia
renal. Destacó que con la presencia de más de 3 de los factores de riesgo
mencionados, la probabilidad de muerte no arrítmica es tan alta que es poco probable
que el implante de CDI mejore la sobrevida de estos pacientes. Finalizada la
conferencia, se le preguntó al Dr. Gersh a qué grupo de pacientes trataría
solo con revascularización para prevención de MS. Respondió que si se
encontrara frente a un paciente que se presenta con dolor torácico de
esfuerzo, MS presenciada en FV y demostración de trombo intracoronario, ese
sería el único caso en que cree que no implantaría un CDI además de la
revascularización. Apéndice Long-term outcomes of
out-of-hospital cardiac arrest after successful early defibrillation.
N Engl J Med. 2003 Jun 26;348(26):2626-33. Bunch TJ, White RD, Gersh
BJ, Meverden
RA, Hodge DO, Ballman
KV, Hammill
SC, Shen
WK, Packer DL. BACKGROUND: Mortality after out-of-hospital cardiac arrest from
ventricular fibrillation is high. Programs focusing on early defibrillation
have improved the rate of survival to hospital discharge. We conducted a
population-based analysis of the long-term outcome and quality of life of
survivors. METHODS: All patients who had an out-of-hospital cardiac arrest
between November 1990 and January 2001 who received early defibrillation for
ventricular fibrillation in Olmsted County, Minnesota, were included. The
survival rate was compared with that of an age-, sex-, and disease-matched
(2:1) control population of residents who had not had an out-of-hospital
cardiac arrest and with that of age- and sex-matched controls from the
general U.S. population. The quality of life was assessed with use of the
Medical Outcomes Study 36-item Short-Form General Health Survey (SF-36) and
compared with U.S. population norms. RESULTS: Of 200 patients who presented
with an out-of-hospital cardiac arrest with ventricular fibrillation, 145 (72
percent) survived to hospital admission (7 died in the emergency department)
and 79 (40 percent) were neurologically intact (good overall capability or
moderate overall disability) at discharge. The mean (+/-SD) length of
follow-up was 4.8+/-3.0 years. Nineteen patients died after discharge from
the hospital. The expected five-year survival rate (79 percent) was identical
to that among age-, sex-, and disease-matched controls (P=0.68) but lower
than that among the age- and sex-matched U.S. population (86 percent,
P=0.02). Fifty patients completed SF-36 surveys at the end of follow-up, and
the majority had a nearly normal quality of life, with the exception of
reduced vitality. CONCLUSIONS: Long-term survival among patients who have
undergone rapid defibrillation after out-of-hospital cardiac arrest is
similar to that among age-, sex-, and disease-matched patients who did not
have out-of-hospital cardiac arrest. The quality of life among the majority
of survivors is similar to that of the general population. N Engl J Med. 1997 Nov 27;337(22):1569-75. BACKGROUND: Patients with coronary heart disease, left ventricular
dysfunction, and abnormalities on signal-averaged electrocardiograms have an
increased risk sudden death. We evaluated the effect on survival of the
prophylactic implantation of cardioverter-defibrillators in such patients at
the time of coronary-artery bypass surgery. METHODS: Over the course of five
years, 37 clinical centers screened all patients who were scheduled for
elective coronary bypass surgery. Patients were eligible for the trial if
they were less than 80 years old, had a left ventricular ejection fraction of
less than 0.36, and had abnormalities on signal-averaged electrocardiograms.
We identified 1422 eligible patients, enrolled 1055, and randomly assigned
900 to therapy with an implantable cardioverter-defibrillator (446 patients)
or to the control group (454 patients). The primary end point of the study
was overall mortality, and the two groups were compared in an
intention-to-treat analysis. RESULTS: The base-line characteristics of the
two groups were similar. During an average follow-up of 32+/-16 months, there
were 101 deaths in the defibrillator group (71 from cardiac causes) and 95 in
the control group (72 from cardiac causes). The hazard ratio for death from
any cause was 1.07 (95 percent confidence interval, 0.81 to 1.42; P=0.64).
There was no statistically significant interaction between defibrillator
therapy and any of 10 preselected base-line covariates. CONCLUSIONS: We found
no evidence of improved survival among patients with coronary heart disease,
a depressed left ventricular ejection fraction, and an abnormal
signal-averaged electrocardiogram in whom a defibrillator was implanted
prophylactically at the time of elective coronary bypass surgery. Prophylactic use of an implantable
cardioverter-defibrillator after acute myocardial infarction. DINAMIT Investigators Hohnloser SH, Kuck
KH, Dorian P, Roberts RS, Hampton JR, Hatala
R, Fain E, Gent M, Connolly SJ; DINAMIT Investigators. N Engl J Med. 2004 Dec 9;351(24):2481-8. BACKGROUND: Implantable cardioverter-defibrillator (ICD) therapy has
been shown to improve survival in patients with various heart conditions who
are at high risk for ventricular arrhythmias. Whether benefit occurs in
patients early after myocardial infarction is unknown. METHODS: We conducted
the Defibrillator in Acute Myocardial Infarction Trial, a randomized,
open-label comparison of ICD therapy (in 332 patients) and no ICD therapy (in
342 patients) 6 to 40 days after a myocardial infarction. We enrolled
patients who had reduced left ventricular function (left ventricular ejection
fraction, 0.35 or less) and impaired cardiac autonomic function (manifested
as depressed heart-rate variability or an elevated average 24-hour heart rate
on Holter monitoring). The primary outcome was mortality from any cause.
Death from arrhythmia was a predefined secondary outcome. RESULTS: During a
mean (+/-SD) follow-up period of 30+/-13 months, there was no difference in
overall mortality between the two treatment groups: of the 120 patients who
died, 62 were in the ICD group and 58 in the control group (hazard ratio for
death in the ICD group, 1.08; 95 percent confidence interval, 0.76 to 1.55;
P=0.66). There were 12 deaths due to arrhythmia in the ICD group, as compared
with 29 in the control group (hazard ratio in the ICD group, 0.42; 95 percent
confidence interval, 0.22 to 0.83; P=0.009). In contrast, there were 50
deaths from nonarrhythmic causes in the ICD group and 29 in the control group
(hazard ratio in the ICD group, 1.75; 95 percent confidence interval, 1.11 to
2.76; P=0.02). CONCLUSIONS: Prophylactic ICD therapy does not reduce overall
mortality in high-risk patients who have recently had a myocardial
infarction. Although ICD therapy was associated with a reduction in the rate
of death due to arrhythmia, that was offset by an increase in the rate of
death from nonarrhythmic causes. Copyright 2004 Massachusetts Medical
Society. Recurrent infarction causes the most deaths
following myocardial infarction with left ventricular dysfunction.
Am J Med. 2005 Jul;118(7):752-8. Orn S, Cleland JG, Romo
M, Kjekshus
J, Dickstein K. PURPOSE: The development of left ventricular systolic dysfunction or
heart failure following an acute myocardial infarction (MI) is a powerful
marker of an adverse prognosis. Recurrent MI could be an important cause of
death, either directly or by provoking arrhythmias. METHODS: The OPTIMAAL
trial randomized 5477 patients with heart failure or evidence of left
ventricular dysfunction following acute MI to losartan or captopril. Over a
follow-up of 2.7 years, there were 946 deaths. Of the 180 (19%) of these
deaths for which autopsy reports were available, acute MI was found in 57%
(102 of 180) of the autopsies. By comparison, an endpoints adjudication
committee using clinical data attributed death to acute MI in only 29 cases.
An acute MI was found at autopsy in 55% (37 of 67) of the deaths that had
been classified as due to an arrhythmia and in 81% (21 of 26) of the deaths
classified as due to progressive heart failure. Including autopsy diagnoses,
the rate of acute MI in patients who died suddenly was independent of the
time elapsed since the index MI, but in patients not classified as dying
suddenly, there was a time-related decrease in recurrent MI from 78% in the
first 30 days to 30% by the end of follow-up. However, only 19% of patients
who died underwent autopsy, so recurrent MI may have been substantially more
common and perhaps had a different relation to time since the index MI if
more patients had undergone autopsy. CONCLUSIONS: In patients with evidence
of major cardiac dysfunction after MI, recurrent MI found at autopsy is
common and has often not been clinically detected. J Am Coll Cardiol. 2008 Jan 22;51(3):288-96. Goldenberg I, Vyas
AK, Hall WJ, Moss AJ, Wang H, He H, Zareba
W, McNitt
S, Andrews ML; MADIT-II Investigators. OBJECTIVES: The study was designed to develop a simple risk
stratification score for primary therapy with an implantable
cardioverter-defibrillator (ICD). BACKGROUND: Current guidelines recommend
primary ICD therapy in patients with a low ejection fraction (EF). However,
the benefit of the ICD in the low EF population may not be uniform. METHODS:
Best-subset proportional-hazards regression analysis was used to develop a
simple clinical risk score for the end point of all-cause mortality in
patients allocated to the conventional therapy arm of MADIT (Multicenter
Automatic Defibrillator Implantation Trial)-II after excluding a
pre-specified subgroup of very high-risk (VHR) patients (defined by blood
urea nitrogen [BUN] >or=50 mg/dl and/or serum creatinine >or=2.5
mg/dl). The benefit of the ICD was then assessed within risk score categories
and separately in VHR patients. RESULTS: The selected risk score model
comprised 5 clinical factors (New York Heart Association functional class
>II, age >70 years, BUN >26 mg/dl, QRS duration >0.12 s, and
atrial fibrillation). Crude mortality rates in the conventional group were 8%
and 28% in patients with 0 and >or=1 risk factors, respectively, and 43%
in VHR patients. Defibrillator therapy was associated with a 49% reduction in
the risk of death (p < 0.001) among patients with >or=1 risk factors (n
= 786), whereas no ICD benefit was identified in patients with 0 risk factors
(n = 345; hazard ratio 0.96; p = 0.91) and in VHR patients (n = 60; hazard
ratio 1.00; p > 0.99). CONCLUSIONS: Our data suggest a U-shaped pattern
for ICD efficacy in the low-EF population, with pronounced benefit in
intermediate-risk patients and attenuated efficacy in lower- and higher-risk
subsets. |
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NOTICARDIO2009 Edición:
Dres.
Oscar Bazzino, Gonzalo Varela, Gustavo Vignolo, Sr. Roberto Aguayo Cronistas:
Dres.
Ignacio Batista, Agustina Bonino, Zully Cortellezzi, Leandro Jubany, Natalia
Lluberas, Gabriel Parma - Producción: César Zignago Sociedad Uruguaya de Cardiología - www.suc.org.uy - Secretaría Congreso: cardio2009@atenea.com.uy |
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